The People's Liberation Army expelled an Australian warplane which intruded into the airspace over China's Xisha Islands on Sunday, a Chinese military spokesperson said on Monday.

The PLA Southern Theater's Air Force spokesperson Li Jianjian said in a statement that on Sunday an Australian P-8A military aircraft illegally made the intrusion without approval from the Chinese government.

The Southern Theater Command organized naval and air forces to track, monitor, take countermeasures and warn off the aircraft in accordance with regulations and the law, Li said.

The spokesperson said the Australian's actions seriously infringed on China's sovereignty and risked causing maritime and air incidents.

"We sternly warn the Australian side to immediately stop its infringements and provocations," Li said. "The theater forces remain on high alert at all times and will firmly safeguard national sovereignty and security as well as regional peace and stability."